Autoradiographic studies using 3H uridine in the salivary glands of three bugs, Lethocerus indicus, Laccotrephes rubra and Antilochus coqueberti show that the nuclei play an important role in contributing RNA. The labelled materials are seen to move into the lumen from the epithelia. RNA shows a tendency to accumulate in the lumen with ascending incubation periods. This behaviour in conjunction with its nucleolar genesis indicates its nature as rRNA. It is also believed that RNA might conjugate with some of the protein available in the lumen to produce RNP.